DERMAPTERA

78

SMITHSONIAN MISCELLANEOUS

COLLECTIONS VOL. 95

NO. 14 INSECT

ABDOMEN

SNODGRASS 79 tracted with the eversion of the end-sac.

The

ductus ejaculatorii, though independent for

some

distance before entering the penes, are united anteriorly in a ductus conjunctus (Dejcn), which takes its origin ina sachkeseminal reservoir (rs) that receives the

two

vasa deferentia (Vd).

Fig. 27.

—

Hexapoda-Dermaptera: threetypesofstructureinthemalegenital exit system and the intromittent organ. (Diagrams based on Meinert, 1864,

1868; Jordan,1909; Heymons, 1912; Walker, 1922; Snodgrass, 1935.) A, Labiduroidca,penes separatebeyond common basal apodeme. B, Hcmi- mcrus talpoides, penesunited, but bothexit ducts retained. C, Forficuloidea, penesunited,onlyone functionalduct.

a, median lobe of penis; aa, median lobe of conjoined penes; Ap, basal apodemal plate ofpenes or penis; b,paramerelobeof penis; c, eversibleend- sacof penis: cc, end-sac of conjoined penes; Dcj, ductus ejaculatorius; dej, nonfunctionalbranchofejaculatoryduct; Dejcn,ductus ejaculatorius conjunctus;

Pen,penis; rs, seminal reservoir; Vd,vas deferens; Vdcn, vas deferens con- junctum; Vsm,vesicula seminalis; x-x, anterior wallof genitalchamber.

In

Hemimcnis

and Forficuloidea the penis is a single structure (fig. 27B, C), but, since it is

armed

with two paramere processes (b, b) arising at the sides of a medianterminal lobe (aa) contain- ingan eversible end-sac (cc), therecan beno doubt that the organ hasbeenproduced bytheunionof

two

penes havingthe structure of thepairedorgansofLabiduroidca (A).

Two

ductusejaculatorii tra- verse the penis of

Hemimcnis

^talpoides (B, Dej), butthey fork in

8o SMITHSONIAN MISCELLANEOUS

COLLECTIONS VOL. 95 the base of the penis

from

a ductus conjunctus (Dejcn) that pro- ceeds

from

a seminal reservoir (rs), intowhich the vasadeferentia dischargebya

common

duct

(Vdcn)

after first enlarging as a pair of seminal vesicles (see Jordan, 1909,

Heymons,

1912).

The

two exitducts of

Hemimerus

openseparatelyintotheend-sac of thepenis, which is

shown

everted in the diagram (B, cc). In Forficula (C), as described by Meinert (1864) and by

Walker

_(1922), the vasa deferentiadischarge separatelyintotheseminalreservoir,andasingle outlet duct (Dejcn) proceeds posteriorly

from

the latter but soon divides into

two

branches;one branch (dej),however,isrudimentary andhas

no

distalconnection, the other (Dej) traverses the penis as the functional ductand opensinto the eversible end-sac (cc).

The

presence of arudimentaryejaculatoryductintheForficuloidea leaves little doubt that the structure of the male organs in Labi- duroidea (fig.27

A)

represents the

more

generalizedcondition inthe Dermaptera, and that the imperfectly unified organs of the other groups (B,

C)

have been derived

from

completely pairedstructures.

In

Hemimerus

the terminal parts of both exit ducts remain func- tional in association with a penis conjunctus; in Forficuloidea one ductis functionallysuppressed. This

manner

of transition within the

Dermaptera from

paired penes withindividual exitductsto a single intromittentorgan with onefunctional ductmightbesupposedto

show

the

method

by which the median penis (phallus) and single exit apparatusof othermaleinsectshasbeen evolved.

There

is,however, nospecificevidence of the production of amedianintromittentorgan by the union of paired penes in any insects other than Dermaptera and Ephemeroptera, andinthese

two

ordersaunionof thepeneshas taken place quite independently. Moreover, the ontogenetic develop-

ment

of the

common

ductus ejaculatorius of otherinsectsshowsthat thisduct,

from

its inception, is an independent median ingrowth of the ectoderm, and suggests that it probably originated phylogeneti- callyasaninvaginationof thebodywallattheapproximated

mouths

of thelateralducts,asitdoesintheontogenyofThysanura.

PLECOPTERA

The

Plecopterain

some

respects

may

present a fairly generalized condition of the specialized organization of the wing-flexinggroup of pterygote insects; but the male reproductive organs are in no

way

generalized, and they furnish no lead toward the evolution of the genitalia inhigherinsects. Infact, the structures that

form

thebasis for most of the elaboration in the external genital

mechanism

of

NO. 14 INSECT

ABDOMEN

SNODGRASS 81 other insectsare either reduced or suppressed in both sexes of the stoneflies. In the femalethegonotreme, or vulva,liesabovethe pos- teriormarginof the eighthabdominal segment (fig.29C, Gtr),where

it opens from a small genital chamber containing the oviducal and spermathecal apertures;butanovipositorisentirelyabsent.

The

two smallprocessesborneby^theeighthsternuminfemales ofPteronarcys areclearly not truegonapophyscs, since the latter always arise pos- teriortothesternal plate. In

some

formsthelateraloviducts appear todischarge separately intothe genital

chamber

(vagina), in others theyfirstunitewith a very short oviductus

communis

(see Klapalek, 1896;Mertens, _1923;

Wu,

1923).

The

genital segments of themale havenoappendicularorgansthatcan be referredtosegmentallimbs, comparable with the styli of apterygote insects, Ephemerida, and Orthoptera, or with the movable claspers (harpagones) of other Pterygota.

The

functional intromittentorganisinmostcasesa phal-

licstructure, though a medianprocess of the epiproct has been de- scribed asa^"sperm conveyor^",andinthegenusLeiictraitispossible thata pair of ventral processesof the tenthsegment conductthesperm to the female

from

the malegenital opening situated at their bases.

In the families Pteronarcidaeand Perlidae the " penis^"isprincipally alarge,eversibleendophallicsac,accompaniedor not

by

anectophal- lus^;inthe other families,

Nemouridae

and Capniidae, there

may

be present a short tubular ectophallus,whichcontains theopeningof the genitalexitpassage,but thelatterhas notbeen

shown

tobeeversible.

The

occurrence of " pairedpenes" hasbeenclaimed,but not

demon-

strated.

Whatever

accessory genital structures are present in the Plecoptera aresecondary processes,usually of the tenthand eleventh abdominal segments, but alsoof the eighth and ninth. Information on the exact function of the phallic organs and accessory genital processesinthe orderis far

from

complete.

The

internal reproductive organs of the Plecoptera are highly variableinthe several families,particularlywithrespecttothegroup- ing of the testicular tubules, and in the size and character of the medianexitduct.

The

testeshaveno^peritonealinvestiture,thesperm tubesbeingfree

from

oneanother, as are thetggtubes of theovaries, and, so far as noted, the gonads have no suspensory ligaments in either sex.

Only

in the genus Leuctra (Nemouridae) have the vasa deferentia been described as being independent of each other (Klapalek, 1896; Mertens, 1923)^;insuchcasesthetestesconsist of groupsof slender tubules arising

from

the anteriorendsof the ducts (fig.28A, Tes). In otherformsthevasa deferentia of opposite sides are united;in

some

casestheyhavecoalesced for a considerable length

6

Fig. 28.

—

Hexapoda-Plecoptera^{: internal} male reproductive organs. (A, B, C,and

F

from Klapalek, 1896;

D

fromJunker, 1923;

E

from Schoenemund, 1912;

G

from Mertens, 1923;

H

from

Wu,

1923.)

A,Lcuctranigra, testes interminalgroupsatendsofvasadeferentia,median exitduct veryshort. B,Pcrlodes (Dictyoptcryx) microccphala, vasa deferentia united anteriorly in arch bearingnumerous sperm tubes, connected posteriorly byloopedcommissure (/). C, Tacnioptcryxtrifasciata,sperm tubesinseries onunited anterior parts of vasadeferentia. D, Pcrla marginata,malelarva 12

mm

long, immature testes with ^"male ovaries"

{MOv)

and saclike sperm tubes (ST). E, same, olderlarva,withnumerous egg tubes (ET) onanterior arch of vasa deferentia. F, Capnianigra, single testis formed by lengthwise unionofpartsofvasa deferentia bearingspermtubes. G,Protonemourapraecox, sperm tubesgrouped at unionofvasadeferentia, the latter dischargedirectly intolongmedianexit duct. H,Ncnwuravallicularia,vasa deferentia discharge intoslendermedianduct{dct),whichopensintolargeterminalexitduct (Dct).

I,Acronenria arida,median genital exitapparatus as seen inundisturbed dis- section. _J, same, partsof exit apparatus artificially extended.

Crpt, phallocrypt;Dct, largemedianexitduct; dct,small medianexit duct;

Dcj, ductus ejaculatorius;Enph,endophallus; ET,eggtube;g, genital process oftenth sternum (seefig.29,

M)

;GC,genitalchamber; k,diverticula ofvasa deferentia; I,commissure betweenvasa deferentia;

MOv,

"maleovaries"; ST, spermtube; Tes. testis; Vd,vas deferens;Vsm,vesiculaseminalis;x-x,inner wallofgenitalchamber.

82

NO. 14 INSECT

ABDOMEN

SNODGRASS 83 oftheiranterior parts (F),in othersthey are continuousendto end in an arch over the ahmentary canal (B, C, D, E, G).

The

sperm tubes of the united ducts are either distributed along the lateral or anterior partsof the ducts (B, C,D, E),orthey are clusteredatthe pointofunion (G).

The

various types ofmale organs found inthe order are described andillustrated by Klapalek (1896) and Mertens (1923), and a

more

detailed account of their structure is given by

Schoenemund

(1912) for species of Perla, and by

Wu

(1923) for

Nenwura

vallicularia. In themale of Perla marginata,in whichthe united vasadeferentia

form

a large loop

from

one sidetothe other, the gonadial tubes of the anterior part of the arch, as

shown

by

Schoenemund

(fig. 28E), duringalatelarvalstagetakeontheform of small ovarioles

{ET)

andcontain egglikecells,while those of the lateral parts

form

large ovaltesticular sacs

{ST)

inwhichthe sper- matozoaare developed.

Each

male ovariole, according to Schoene-

mund

(1912) and Junker (1923), has the structure of a^typicalpano-

istic eggtubewithaseries of 12to 18 oocytes enclosed individually in cellular follicles.

At

anearlier larval stage, Junker observed, the eggtubes are enclosed in a pair of ovarial sacs, or ^"maleovaries^"

(D,

MOv),

^{situated on the}medianpart of the arch of the duct,but he says a

few

oocytes aretobefoundalso inthesaclikespermtubes {ST).

The "male eggs"

of Perlamarginata, however, were found byJunkertopossess the diploid

chromosomes

of the spermaticcells

;

they never complete normal maturation, and the tubules containing themdegenerateatthetransformationtotheadult.

The

vasa deferentia are generally enlargedtoward their posterior endsto

form

storagevesiclesfor thespermatozoa (fig.28 A, G,

H,

_J,

Vsm).

In

some

formsa tubular diverticulum _(J,k) isgivenoff

from

eachduct. Klapalekdescribesa conditioninspeciesof severalgenera in which the two ducts areconnected by a transverse vessel (B, /) looped forward between them, which he regards as a vesicula semi- nalis. InLeiictra,accordingtoKlapalekand Mertens, a sperm^vesicle in the

form

of a median pouch arises at the junction of the vasa deferentiawiththe ejaculatory duct (A,

Vsm).

The

median genital exit system of male Plecoptera varies con- siderably

among

^{different genera in the relative} development of its parts, and the identities of the latter are difficultto follow in pub- lished descriptions of the genital organs. In a freshly dissected specimenof Acronciiria (fig.28I)thetwotubular vesiculae seminales

{Vsm)

appear todischargedirectly intoa large sac

{Enph)

opening throughtheectophallus {Phi);butifthe parts are pulled out length- wise (J) ^{it is} seenthatthere are short terminalsections of the vasa

84

SMITHSONIAN MISCELLANEOUS

COLLECTIONS VOL. 95 deferentiabeyondthevesiciilae,whichuniteina slenderductus ejacu- latorius (Dej), andthat thelatteropens intothe anteriorend of the phallicsac (Enph). There canbenoquestion inthisspecies that the terminal sac of the exitsystem is an endophallic invagination from the

mouth

of the external penis, or ectophallus (Phi).

The

endo- phallusiseverted duringcopulation (fig.29 E, Pen), and inthepro- tractedconditionitformsthe principalpart of the intromittent organ.

The

everted ^"penis^"of AcroneuriapaciUca is figured by

Needham

and Claassen (1925), that of Acroneuria evoluta by Clark (1934).

Other species

shown

to have an eversible phallic organ include Pteronarcysnohilis (Prison, 1935), Peria^hastata,Perlodessignatus, and Isoperla fusca

(Needham

and Claassen, 1925).

The

wide exit tube of Chloroperla granvmatica and of Isopteryx tripunctata de- scribed by Klapalek (1896) as the "ductus ejaculatorius" _is very evidentlyaneversiblestructure.

An

eversible endophallus,therefore, isprobablyacharacteristicfeature of the families Pteronarcidaeand Perlidae.

The

walls of the endophallus are mostly

membranous,

but they

may

containscleroticareas orplates,andin

some

formsthey are pro- ducedinto folds or are

armed

witha pair of long rods or hooklike processes, all such structures taking an external position with the eversion of thesac.

The

exposedrods orhooksarecalled"titillators"

bymostwriters,but a rodlike internalarmatureof the endophallus is generally termed a virga (fig. 22B, Vrg), and the

name

^titillator giventoterminal processes of the ectophallus {Ttl).

The

endophallus

may

be a direct invagination

from

the anterior wall of the genital chamber, as

shown

by Klapalek in Chloroperla {Isopteryx) tripunctata, in whichthe long tube, designated ^"ductus ejaculatorius " by Klapalek, opens simply by a wide mouth, from which project the tips of the endophallic rods, or virgae. In other Perlidae,however,anectophallus

may

be present as adistinct" penis^"

projectingintothe genital

chamber

andcontaining the

mouth

of the endophallus.

An

organof thistypeiswell

shown

by

Walker

(1922) in Perla tristisasa large globular structure concealed in the genital

chamber

above the ninth abdominal sternum. In Acroneuria arida (fig.28I,J) the ectophallus (Phi) isathick,conical lobe

somewhat

constrictedatitsbase,with anapicalopeningthat leadsintothewide endophallic sac (Enph).

The

phallus ofthis species, however,isnot seendirectlyon openingthe shallowgenital

chamber

;itisconcealed inadeep pocket (phallocrypt,Crpt) of the genital

chamber

wall,the aperture of which appearsat thebottomofthe external cavity.

The

NO. 14 INSECT

ABDOMEN

SNODGRASS 85 fully everted ^"penis" in this case includes the endophallus, the ectophallus, the phallocrypt, and probably also the shallow genital chamber.

In the families

Nemouridae

and Capniidae^there appearsto beno evidencethatthe functional intromittentorganisanevertedstructure.

The

medianexitductisin

some

cases short andinothers long,and, in species studied, it terminates in an ectophallus, which, however,

may

bevery small.

The

terminalexitduct of

Nemaura

vallicularia, as

shown

by

Wu

(1923), ^is a longmediantube extending forward almosttothe base of the

abdomen

(fig.28

H,

Dct);itis enclosedin a thick sheath of strongmuscular fibers,and ends ina short, taper- ingsclerotic penis.

Opening

intothe anteriorend of thistube,

how-

ever, is a

much

slenderer median duct {dct) that receives the

two

vasa deferentia, asinAcroveiiria _(J,Dej).

We

mightsuspect,there- fore, thatthe large duct of

Nemoura

is a noneversible endophallus, andthat the slender ductisthetrue ductusejaculatorius.

The

internal genitalstructures of

Protoncwoura

praecox, as describedby Mertens (1923), are the same as those of

Nemoura

vallicularia except that here thevasadeferentiadischargedirectly intothe largemediantube, which latter Mertens says has extraordinarily strongmuscular walls and evidently servestoexpel the spermatic^fluid.

A

^similar,strongly muscular exitpassage is present in Taeniopteryx

nmura

and opens through awide, bluntly conical ectophallus.

The

latter is protracted in one specimenobserved,but thereis

no

accompanying'eversion of the duct.

Wu

(1923) describesthe development of theexitduct in

Nemoura from

an invagination of the body wall between the ninth and tenth abdominal sterna, beginning with the ninth instar and increasing in lengthduring subsequent instars. In the earlierstages the vasa deferentia open directly into the median tube, which thus appearsinitsinceptiontobe the ductusejaculatorius.

A

^"diphallic"

condition issaidby

Crampton

(1918) tooccurin

Nemoura

completa, butsincethe structures designated^"penes^"arenotdemonstratedto be such by dissection,

we may

suspect that they are merelyphallic lobes, and that a single genital orifice will be found between them.

In thegenusLeiictra the phallic apparatus is

much

reduced, and

itappearsthat the intromittent function

may

beperformed bya pair of processes arising

from

thesternumof the tenthabdominalsegment.

Thesestructures are describedby KlapaiekinL. nigraandcylindrica, and by Mertens ^{in L.} prima and hippopiis as a pair of sclerotic processes (Chitingraten,Titillatoren) arisingatthesidesof the geni- tal orifice, and embraced by two prolongations of the plates of the tenth sternum.

Each

median process, according to these authors, is

Fig. 29.

—

Hexapoda-Plecoptera: external genitalia.

A, Acroncuria arida, male, end ofabdomen, dorsal view. B,same, ventral view. C, Acroncuria^ female, end of abdomen, ventral view. D, Acroncuria arida,male,endofabdomen,lateralview. E,Acron-curiaevohita,endofabdomen with protracted penis (fromClark, 1934). F,Neophasganophora capitata,end ofabdomen, dorsal view (from Frison, 1935). G,Nemoura ^{bifurcata, end of} abdomen, dorsal view. H, same, supra-anal process, lateral view. I, same, end ofabdomen,ventral view. _J, Pteronarcys proteus,end ofabdomen, lateral view. K, Taeniopteryxnmura, endofabdomen,lateralview. L,Leuctrasibleyi, end ofabdomen, lateral view. M, same, ninthand tenth abdominal segments, ventral view.

a,tergalprocessofeighthabdominalsegment; b,tergalprocessofninthseg- ment;c,percussiondisc ofninth sternum; Cer, cercus; d,basal lobe of ^ninth sternum; c,lateral process oftenth segment; Eppt, epiproct; /,g, lateral and medianventral processesoftenthsternum; Gtr,gonotreme (openingof genital chamber); /;, dorsal process of paraproct;i, median process of epiproct;IX, ninth abdominal segment; Papt, paraproct; Pen, penis (protracted phallic organs);Phi, ectophallus;S,sternum;T,tergum; X,tenthabdominalsegment;

X.V,membranousventeroftenth segment.

86

NO. 14 INSECT

ABDOMEN

SNODGRASS 87 grooved on its inner surface, the two apposed processes thus form- ing a channelthroughwhichthe spermaticfluidisconveyed

from

the ejaculatory duct.

The

four processes are well developed inLeuctra siblcyi (fig. 29

M,

/,g),in whichcollectively theyappearas a large

arm

projecting anteriorly above the end of the

abdomen from

the up-turned sternum of the tenth segment (L).

The

longer median in-ocesses

(M,

_{g) are}flattened and slightly concaveontheirapposed faces,and aremovablyattachedat theirbasesinnotches of the tenth sternal plates

(XS). The

slenderer, tapering lateral processes (/) aredirect continuations of thesternal plates, but,

owing

to a partial membranization of thelatter, theycan be turnedoutward by sternal muscles inserted laterad of their bases.

The

genital opening of L.sibleyiappearstobeon asmall phallicpapilla (L,

M,

Phi) inthe

membranous

area between the ninth and tenth abdominal sterna at apoint wherethedischarged

sperm

mightenterthe channel between the sternalprocesses of the tenth segment.

The

median exit ductis

shown

by Klapalek and by Mertens to be very short in species of Leuctra (fig.28

A),

with amedianstalked " vesicula seminalis" aris- ing

from

itatthe junction with the vasa deferentia.

The

externalgenitalarmatureofmalePlecopteraconsistsof secon- dary outgrowths or lobes of the posterior abdominal segments.

Though some

of these structures aremovable byaspecialadaptation of thesegmentalmuscles,itisclear thatnone of

them

represents the styliofthe apterygoteinsectsandOrthoptera, or thestylusderivatives inthe

form

of independentlymusculatedclaspers, or harpagones, of the

Ephemerida

andhigherinsects,whichso

commonly

are themost important features of the periphallic genitalia. In the evolution of the Plecoptera, therefore, the usual accessory genital structures, in- cluding the ovipositor of the female,have beendiscarded,andinthe male therehas been developed a profusion of secondary structures.

The

principal accessory genital developments of male stoneflies pertaintothetenthandeleventhabdominalsegments, butlesserstruc- tures occur frequently on the ninth segment, and sometimes on the eighth.

Among

the species hereillustrated, examplesof tergal proc- esses on the eighth and ninth segments are seen in Leuctra sibleyi (fig. 29L, a) andinPteronarcysproteus _(], b). InAcroneuria the ninth sternum bears a smooth round or oval elevation near its pos- teriormargin (B,D,E,c)

known

asthe percussiondisc,or

hammer,

withwhichthemaleissaidto

make

a

drumming

sound bytapping

on

the surface beneath

him

(see

Macnamara,

1926).

Most

of the

Nemouridae

have a small elongate ventral lobeflexibly attached to thebase of the ninthsternum (I, K, L,

M,

d).

The

posteriormargin